Comparison of the solubility of PVF and PVDF in supercritical CH2F2 and CO2 and in CO2 with acetone, dimethyl ether, and ethanol

Cloud-point data are reported at temperatures to 245 degrees C and pressure s to 2700 bar for poly(vinyl fluoride) (PVF) and poly(vinylidene fluoride) (PVDF) in CO2, CH2F2, dimethyl ether (DME), acetone, and ethanol and in mix tures of CO2 with acetone, DME, and ethanol. PVF does not dissolve in CO2 e ven at 245 degrees C and 2700 bar, but, PVF does dissolve in CH2F2 at 180 d egrees C and pressures in excess of 1500 bar. To dissolve PVF in DME, press ures in excess of 550 bar and temperatures in excess of 130 degrees C are n eeded although it only takes similar to 100 bar to maintain a single phase to temperatures of similar to 220 degrees C with ethanol and acetone. Compa red to the conditions needed to dissolve PVF, it takes hundreds of bar less pressure to dissolve PVDF in CO2, CH2F2, and DME and similar to 60 bar les s pressure to dissolveit in acetone, but it does take similar to 60 bar mor e pressure to dissolve it in ethanol. With CO2, ethanol is a better cosolve nt than acetone for both fluoropolymers at high temperatures and at low eth anol concentrations. However, when the temperature is decreased or the etha nol concentration is increased, it acts as an antisolvent probably due to e thanol self-association, Compared to ethanol and acetone, DME is not as goo d a cosolvent more than likely as a result of its lower density and smaller dipole moment. For all three cosolvents, their impact on the reduction of the cloud-point pressure diminishes with increasing cosolvent concentration . It is also evident that CO2 is an effective antisolvent since small amoun ts of it added to the polymer-cosolvent mixtures greatly increase the press ures needed to obtain a single phase.